Core C (Pipkin) The overarching goal of Core C is to provide standardized, uniform and innovative next generation sequencing (NGS) and computational approaches to address the genome-scale experiments proposed in Projects 1-3. The individual Projects goals are to analyze pooled in vivo screens, gene expression, transcription and chromatin structure and to discern the basic molecular regulation of T and B cell mediated immunity. Core C will facilitate these objectives by using NGS approaches to analyze (1) pooled in vivo gene loss-of-function screens by sequencing, (2) expression of chromatin-associated RNA (nascent RNA), and mature mRNA from limiting ex vivo cell numbers, and single cells (scRNA-seq) using RNA-seq; (3) chromatin accessibility via the assay for transposase-accessible chromatin followed by sequencing (ATAC-seq), and nucleosome organization (MNase- seq and BEM-seq); and (4) CRF and TF binding to near base-pair resolution after chromatin immunoprecipitation from small numbers of primary lymphocytes using ChIP-exo (Aims 1 and 2). Core C has demonstrated experience in developing and applying all of these approaches. In addition, Core C has established a centralized, interlinked and documented framework for the storage, analysis and sharing of these large datasets between Projects 1-3 (Aim 3), and will apply available algorithms in creative arrangements that comprise computational approaches to identify and define operational cis-regulatory regions based on chromatin accessibility, nucleosome organization and histone modifications, and to infer utilized TF binding site motifs within these regions and predict their cognate TFs. Furthermore, these observations will be correlated with transcriptional activity (nascent RNA expression) and RNA Pol II activity (ChIP-seq) and TF and CRF binding events (ChIP- exo), and overall gene expression (mRNA) in the context of gene-perturbations to clarify functionally how gene regulatory networks drive T cell differentiation and function during immune responses in vivo.